The interference management in wireless communication systems is central to the performance of the communication system and highly dependent on the specific air interface. While OFDMA transmissions will be discussed, similar considerations affect (W)CDMA systems with same cell interference Isc cancellation. Therefore for both (W)CDMA and precoded OFDMA, the dominant interference is other cell interference Ioc that results from the transmissions to/from other users in adjacent cells. Lately, the notion of heterogeneous networks (HTN) was introduced that encompasses multiple stacked cell layers.
In the HTN deployment scenarios the notion that same cell interference is negligible must be revisited as the small cells are usually under the coverage of a larger macrocell and in general reuse macrocell resources with either hard or soft reuse patterns. Small cells may include picocells, femtocells, relay nodes and in general any node that defines explicitly or implicitly a new cell. Interference management is possible by controlling the transmit power spectral density of mobiles in the uplink (UL) and evolved Node-Bs (eNB) in the downlink (DL). Interference variability is dependent on many factors such as:                The decorrelation length of the shadowing component. This defines how often the long-term channel will vary over time.        The power control of interfering sources.        The transmission times of the packets of the interfering sources as determined by the application (e.g., equal global quality of service (GoS or eGos), Best Effort, Streaming Video) or by the scheduler.        The presence of any MIMO transmission schemes such as Closed Loop Multiuser MIMO (MU-MIMO) where resources are reused spatially.        The diversity order of the interfering sources, which is a quantity that affects the degrees of freedom of interference and therefore its statistics. Diversity order may increase due to the MIMO mode used (SFBC), due to precoding or due to the specific resource allocation.        
Controlling transmit power spectral density is based on the following capabilities:                Each node (macro or small cell) explicitly or implicitly using the nearby UEs, measuring the other cell interference and exchanging this information within the Radio Access Network (RAN).        Transmitting this information to a computing resource that can be part of a cloud computing architecture where further processing such as parameter inference, as well as interference information compression can take place.        
In view of the above, and other concerns, numerous interfaces are established between the macro and/or small cells to convey the messages reporting the above described information.
FIG. 1 illustrates a portion of a conventional heterogeneous network (HTN) having multiple stacked cell layers. FIG. 1 shows the coverage area of a macro cell served by a macro base station 10 also called an evolved NodeB or eNodeB. As shown, the coverage area includes a network 15 of pico cells, each served by a pico base station 20 also called a pico evolved NodeB or pico eNodeB. User equipment (UE) 25 falls within the coverage area of one or more of the pico base stations 20 and therefore the coverage area of the macro base station 10. The communication needs of the UE may be served by one of the communication nodes—pico base stations 20 or macro base station 10. If served by a pico base station 20, the UE's traffic may traverse the pico network 15 (i.e., from pico eNodeB to pico eNodeB) to a gateway 40, and from the gateway 40 to other networks and/or the internet. Also, the UE's traffic may traverse the pico network 15 to the macro base station 10, and from the macro base station 10 to other networks and/or the internet. Still further, the UE's traffic may flow directly to and from the macro base station 10. As will be appreciated additional and/or different network layers may be present. For example, in addition to or instead of the pico network 15, a Femto network may exist or individual Femto cells may exist.
In today's networking architecture for small cells, a well-known X2 interface is established between the small cell of interest and each neighboring small cell. These X2 interfaces are called the intra-layer X2 interfaces. As shown in FIG. 1, this forms an X2 interface cloud among the pico base stations 20. Similarly, an X2 interface between the small cell of interest and each neighboring macrocell are set up. These X2 interfaces are called the inter-layer X2 interfaces. This is also shown in FIG. 1, with the macro base station 10 having N X2 interfaces with N pico base stations 20. The X2 interfaces carry information such as for managing interference from base station to base station. With the interference problem far worse in HTNs, exchanging information as described above to manage the interference problem becomes more critical. However, with field site-to-site distances for the 700 MHz band on the order of 2 km, for example, the number of potential small cells could be in the tens or even hundreds depending on their power levels and their associated coverage. As result, the number of X2 interfaces rapidly becomes very high.